Abstract: The teachings of present disclosure may be embodied in gas sensors for detecting oxygen and methods for detecting oxygen in a gas mixture. For example, a gas sensor for detecting oxygen in a gas mixture may include: an oxygen ion conductor; at least two electrodes arranged on the oxygen ion conductor, the at least two of the electrodes arranged to come into contact with the gas mixture during operation of the gas sensor; a control device applying a polarization voltage or a polarization current to the at least two electrodes during a polarization period; a measuring device for measuring the current or the voltage at the at least two electrodes; and an evaluation device for calculating the oxygen content from the measured voltage or the measured current. Calculating the oxygen content may be based on: a current measured during the polarization period, or a charge which has flowed over the polarization period, or a voltage measured directly after the polarization period.